Stringer, M. J. and Benson, A. J. and Bundy, K. and Ellis, R. S. and Quetin, E. L. (2009) Mock observations with the Millennium Simulation: cosmological downsizing and intermediate-redshift observations. Monthly Notices of the Royal Astronomical Society, 393 (4). pp. 1127-1140. ISSN 0035-8711 http://resolver.caltech.edu/CaltechAUTHORS:20091006-151109583
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Only by incorporating various forms of feedback can theories of galaxy formation reproduce the present-day luminosity function of galaxies. It has also been argued that such feedback processes might explain the counterintuitive behaviour of 'downsizing' witnessed since redshifts z ≃ 1–2. To examine this question, observations spanning 0.4 < z < 1.4 from the Deep Extragalactic Evolutionary Probe (DEEP)2/Palomar survey are compared with a suite of equivalent mock observations derived from the Millennium Simulation, populated with galaxies using the galform code. Although the model successfully reproduces the observed total mass function and the general trend of 'downsizing', it fails to accurately reproduce the colour distribution and type-dependent mass functions at all redshifts probed. This failure is shared by other semi-analytical models which collectively appear to 'over-quench' star formation in intermediate-mass systems. These mock lightcones are also a valuable tool for investigating the reliability of the observational results in terms of cosmic variance. Using variance estimates derived from the lightcones, we confirm the significance of the decline since z ∼ 1 in the observed number density of massive blue galaxies which, we argue, provides the bulk of the associated growth in the red sequence. We also assess the limitations arising from cosmic variance in terms of our ability to observe mass-dependent growth since z ∼ 1.
|Additional Information:||© 2009 The Authors. Journal compilation © 2009 RAS. Accepted 2008 November 4. Received 2008 November 3; in original form 2008 June 12. We would like to thank Carlton Baugh, Richard Bower, Shaun Cole, Carlos Frenk, John Helly, Cedric Lacey and Rowena Malbon for allowing us to use the GALFORM semi-analytic model of galaxy formation (www.galform.org) in this work. We also thank Simon White for helpful comments. The Millennium Run simulation used in this paper was carried out by the Virgo Supercomputing Consortium at the Computing Centre of the Max-Planck Society in Garching. The data bases and the web application providing online access to them were constructed as part of the activities of the German Astrophysical Virtual Observatory http://www.g-vo.org/Millennium. MJS acknowledges support from the Warden and Fellows of New College, Oxford, the hospitality of the CTCP at Caltech and of the KITP, Santa Barbara. AJB acknowledges support from the Gordon & Betty Moore Foundation. RSE acknowledges financial support from the Royal Society.|
|Subject Keywords:||galaxies: evolution; galaxies: formation; galaxies: luminosity function, mass function; galaxies: stellar content|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Ruth Sustaita|
|Deposited On:||07 Oct 2009 15:10|
|Last Modified:||26 Dec 2012 11:26|
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